American Board of Internal Medicine (ABIM) Certification Practice Exam

Prior to testing for H. pylori, H2 blockers should be avoided for how many days?

1. 1 day

2. 2 days

3. 3-5 days

4. 7 days

The correct answer is: 2 days

H2 blockers should be avoided for a minimum of 2 days prior to testing for H. pylori because these medications can interfere with the accuracy of certain testing methods, particularly the urea breath test and potentially even the endoscopic biopsies used for culture and histology. H2 blockers suppress gastric acid secretion, which can affect the viability of H. pylori and potentially lead to false-negative results. By allowing a gap of at least 2 days, the gastric pH can return to a more acidic state, increasing the likelihood that H. pylori is present and detectable during the testing process. This two-day abstention balances the need for accurate testing with the pharmacokinetics of H2 receptor antagonists, which typically do not completely clear from the system immediately after ceasing administration. Opting for shorter durations, such as one day, may not be sufficient for the medication to clear effectively enough to ensure the accuracy of test results, while a longer duration like a full week may be unnecessarily prolonged. Thus, the recommendation aligns closely with evidence supporting 2 days as an optimal duration for avoiding H2 blockers before testing.